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Jun 2001
Inlets
Agilent 6890 Gas Chromatograph Service Manual
230 Cool On-Column Inlet
Programmable Cool On-Column (PCOC) inlets are designed to allow the
injection syringe to deposit the liquid sample directly into the capillary
column. This is accomplished by the use of an insert which serves to align the
syringe with the capillary column and the syringe needle.
Theory of operation
At injection, liquid sample is introduced directly into the column.
• For manual injections, a duckbill valve (isolation valve) uses inlet
pressure to create a pneumatic seal around the needle.
• For automatic injections, the duckbill valve is replaced with a septum
and nut and the septum maintains the pressure seal.
For both manual and EPC inlets, the flow paths are the same; the flow is
divided into two streams. The carrier gas enters the inlet and flows into the
column and additionally provides for a constant septum purge flow regardless
of the column flow rate you use.
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